1. Field of the Invention
The present invention relates to sampling probes. More particularly, the present invention relates to sampling probes used to collect samples of a powder blend in pharmaceutical applications. While the invention is subject to a wide range of applications, it is especially suited for use in an apparatus or in a process; and it will be particularly described in that connection.
2. Description of Related Art
It is a requirement for pharmaceutical companies to collect samples of a powder blend and demonstrate that the blend is homogeneous. A device known as a sampling probe or xe2x80x9cthiefxe2x80x9d is used to collect such powder samples from a large blender. All of the samples must contain appropriate amounts of particular drugs in order for the blend to be classified as homogenous. A process has been proposed in which a sampling probe shown in FIG. 1 is introduced into a powder blend. This sampling probe has concentric inner and outer tubes, wherein the inner tube has an opening covered by the outer tube. The outer tube is rotated to uncover the opening in the inner tube. The powder blend then flows into the inner tube and the outer tube is then rotated once again to cover the opening, thereby trapping the powder to collect a sample.
However, when the powder blend segregates easily, the captured sample is sometimes not representative of the blend. That is, certain particles in the blend separate as the sample flows into the probe and is collected. The sample could then contain either too much or too little of a particular component of a drug. Thus, a homogeneous blend may possibly be characterized erroneously as being non-homogeneous. Failure of a blend to meet FDA homogeneity requirements can represent considerable financial hardship to a pharmaceutical company.
FIGS. 2 and 3 show other embodiments of sampling probes proposed for use in the pharmaceutical industry. These sampling probes have drawbacks similar to those associated with the sampling probe shown in FIG. 1. In particular, these probes could also allow for powder segregation, thereby providing a false indication of homogeneity/non-homogeneity. Thus, there is a need for an improved sampling probe capable of collecting samples from powder blends that segregate easily.
Accordingly, the present invention is directed to an improved sampling probe capable of collecting samples from powder blends that segregate easily. The invention further provides a means of collecting samples by xe2x80x9cgrabbing,xe2x80x9d entrapping or enclosing a predetermined volume of powder blend from anywhere in the powder blender without having the blend flow into the probe.
Additional features and advantages of the invention will be set forth it the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the written description and claims herein as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention includes a sampling probe having a housing defining a trough with an opening. At least a portion of the opening is in the direction of the probe""s insertion. The probe also has a comer axially movable with respect to the housing between an open position in which a substance is allowed to pass into the trough and a closed position in which the cover covers the opening to retain a predetermined volume of the substance in the trough. A guide is configured to guide axial movement of the cover between the open and closed positions.
In another aspect, the sampling probe""s cover is flexible and the guide is configured to direct the cover in a curved path.
In yet another aspect, the sampling probe""s housing has a first and second inner wall surfaces spaced from one another. The surfaces define at least a portion of the trough between them. The guide is formed by a first groove on the first inner wall surface and a second groove on the second inner wall surface.
In another aspect, the invention includes first and second removable plates. The first plate rests on the first inner wall surface and the second plate rests on the second inner wall surface.
In yet another aspect, the sampling probe includes a housing with a first inner wall surface having a first edge and a second edge and a base parallel to the first inner wall surface and having a first edge and a second edge. The first edge of the base is coupled to the first edge of the first inner wall surface. The housing also has a second inner wall surface parallel to the first inner wall surface and having a first edge and a second edge. The first edge of the second inner wall surface is coupled to the second edge of the base. The first inner wall surface, second inner wall surface, and base define a trough with an opening. The probe also has a flexible cover movable with respect to the housing between an open position permitting entry of substances into the trough via the opening, and a closed position closing the opening to retain a predetermined volume of the substance in the trough. A guide is configured to guide movement of the cover between the open position and the closed position.
In another aspect, the guide in the sampling probe is a set of grooves. A first groove is on the first inner wall surface and a second groove is on the second inner wall surface. The grooves face each other and are in engagement with the cover.
In yet another aspect, the cover is attached to a spring biasing the cover towards one of the open or closed positions. The cover may also be coupled to a handle.
In another aspect, the probe""s housing includes a cavity configured to store at least a portion of the cover when the cover is in the open position. The housing may also have a bracket including first and second sides and a base.
Another aspect of the invention is a method of obtaining a sample of a substance such as a powderous material. The method includes providing any embodiment of the sampling probe summarized above, inserting the sampling probe into the substance while the cover is in the open position so that a portion of the substance enters the trough, and moving the cover to the closed position to retain a predetermined amount of the substance in the trough.
In another aspect, the method includes biasing the cover toward one of the open and closed positions.